I suggest you ...

Note Icon displays Markup Style

Within the note/highlight document, the marked up content icon (far left) should default to the markup type used to make the note. This would allow for quick scanning based on the type of highlight (because many people highlight with different markup for difference significances).

The icon already shows the color and indicator icon style chosen for the current note. How would you envision the markup style actually being shown? The previews shown in the Highlighting panel are rather large; it seems like it would be extremely cluttered if they were shown next to each note. Or did you have something else in mind?